Rogues will roll just like everyone else, besides, even if the person who wins it is not an engineer or blacksmith, they can still get a rogue buddy or ask trade chat to find a rogue to open it for them.

If a lockbox drops from a mob and you have a rogue in the group, does he get priority to get it since hes the only one that can open it? IMO they should since no one else can open it and if there isnt a rogue then you can roll whatever you on it.